Electronic apparatus for vehicle

ABSTRACT

An electronic apparatus for a vehicle, includes an electronic device, a waterproof housing that receives the electronic device, and a filter. The housing has a ventilation hole that penetrates through a housing wall of the housing. The filter is attached to a filter attachment portion of the housing wall to cover the ventilation hole. A wall surface of the ventilation hole includes a slope surface section that has an increasing cross-sectional area, which progressively increases from an inner end to an outer end of the slope surface section toward an outer surface of the housing wall in a penetrating direction of the ventilation hole. Furthermore, a distance between the filter attachment portion and the outer surface is larger than that between the inner end of the slope surface section and the outer surface in the penetrating direction.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of application Ser. No.13/009,054 filed on Jan. 19, 2011 which is based on and claims priorityto Japanese Patent Application No. 2010-41603 filed on Feb. 26, 2010,the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an electronic apparatus for a vehicle.

BACKGROUND OF THE INVENTION

Conventionally, an electronic control unit, which is exposed to ahigh-pressure water flow in washing a vehicle, such as an electroniccontrol unit that is arranged in an engine room of a vehicle andperforms control of an engine is well known. For example, as describedin JP-A-2008-55981 and JP-A-2009-6808, a waterproof housing includes aventilation hole and a sheet-like filter for covering the ventilationhole.

In an electronic control unit (waterproof device) described inJP-A-2008-55981, a filter membrane is attached to an outer surface of acover (waterproof housing) by an adhesive sheet having multiplemicropores so that a ventilation hole (through-hole) is closed. Theadhesive sheet and the filter membrane correspond to the above-describedfilter.

In an electronic control unit (waterproof device) described inJP-A-2009-6808, a recess is formed in an upper surface side of a case(waterproof housing) having a ventilation hole (through-hole) tosurround the ventilation hole, and a sheet-like breathing filter(filter) is attached to a bottom surface of the recess to cover theventilation hole (through-hole).

However, in the configurations described in JP-A-2008-55981 andJP-A-2009-6808, a high-pressure water flow at an unchanged impetus maybe directly poured on the sheet-like filter attached to the waterproofhousing, as described above. Thus, there is a problem that the filter iseasily peeled off.

If the filter is peeled off, water or the like enters into thewaterproof housing, and thus, a short-circuit may occur in a circuitboard or the like, or an electronic device may break down.

SUMMARY OF THE INVENTION

In view of the above-described problem, it is an object of the presentinvention to provide an electronic apparatus for a vehicle, in whichpeel-off of a sheet-like filter due to a high-pressure water flow can beeffectively suppressed.

According to one aspect of the present invention, an electronicapparatus for a vehicle, includes at least one electronic device, awaterproof housing, and a filter. The waterproof housing receives the atleast one electronic device in an interior of the waterproof housing. Aventilation hole penetrates through a housing wall of the waterproofhousing from an inner surface to an outer surface of the housing wall ina penetrating direction thereof to communicate between an outside and aninside of the waterproof housing. The filter is generally planar and isattached to a filter attachment portion of the housing wall to cover theventilation hole. A wall surface of the ventilation hole includes aslope surface section that has an increasing cross-sectional area, whichprogressively increases from an inner end to an outer end of the slopesurface section toward the outer surface of the housing wall in thepenetrating direction of the ventilation hole. A distance between thefilter attachment portion and the outer surface of the housing wallmeasured in the penetrating direction of the ventilation hole is largerthan a distance between the inner end of the slope surface section andthe outer surface of the housing wall measured in the penetratingdirection of the ventilation hole.

In this manner, by configuring the ventilation hole such that thedistance between the filter attachment portion and the outer surface ofthe housing wall is larger than that between the inner end of the slopesurface section and the outer surface of the housing wall in thepenetrating direction of the ventilation hole, it becomes difficult fora high-pressure water flow with a small incident angle to be directlypoured on the filter because of at least a thickness of the slopesurface section in the penetrating direction. That is, it is especiallyimportant to suppress a high-pressure water flow with a large incidentangle (for example, a high-pressure water flow with the incident angleof 90° along the penetrating direction of the ventilation hole) so as torestrain the peel-off of the filter.

In contrast, in the present invention, the wall surface of theventilation hole includes the slope surface section that has theincreasing cross-sectional area, which progressively increases from theinner end to the outer end of the slope surface section toward the outersurface of the housing wall in the penetrating direction of theventilation hole. A high-pressure water flow with a large incident angle(for example, the high-pressure water flow along the penetratingdirection of the ventilation hole) is reflected on the slope surfacesection and the reflected water flows hit against each other above thefilter. Therefore, an impetus (i.e., pressure) of the water flow that isgoing to directly hit against the filter is weakened.

Furthermore, if water is stored in the ventilation hole with the filterused as an end surface, the stored water functions as a cushion againstthe high-pressure water flow. Thus, the high-pressure water flow can berestrained from directly hitting against the filter despite the incidentangle of the high-pressure water flow.

Accordingly, in the waterproof housing, the peel-off of the filter dueto the high-pressure water flow can be restrained.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a perspective view showing a structure of an electroniccontrol unit according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1;

FIG. 3 is an enlarged cross-sectional view showing a ventilation holeand a periphery of a filter;

FIG. 4 is an enlarged plan view showing the ventilation hole and theperiphery of the filter;

FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 4;

FIG. 6 is a cross-sectional view showing the effect of a wall surfaceand an installation structure of the filter shown in FIG. 5;

FIG. 7 is a cross-sectional view showing the arrangement of theventilation hole and the filter with the electronic control unitinstalled to a vehicle;

FIG. 8 is a cross-sectional view showing a modified example of a firstslope surface section;

FIG. 9A is a cross-sectional view showing the effect of the first slopesurface section shown in FIG. 8;

FIG. 9B is a cross-sectional view showing the effect of the first slopesurface section shown in FIG. 5 as a comparative example;

FIG. 10 is a cross-sectional view showing another modified example ofthe first slope surface section;

FIG. 11 is a cross-sectional view showing the effect of the first slopesurface section shown in FIG. 10;

FIG. 12 is a cross-sectional view showing the effect of the first slopesurface section shown in FIG. 10;

FIG. 13 is a cross-sectional view showing a modified example of aconnecting surface section;

FIG. 14 is a cross-sectional view showing the modified example of theconnecting surface section;

FIG. 15 is a cross-sectional view showing the modified example of theconnecting surface section;

FIG. 16 is a table showing details of samples A1 to A8 in samples usedfor a peel test of the filter;

FIG. 17 is a representative view showing the details of the samples A1to A8;

FIG. 18 is a table showing details of samples B and C1 to C3 in thesamples used for the peel test of the filter;

FIG. 19 is a graph showing a relation between a peeled area due to ahigh-pressure water flow and each of the samples A1 to A8, B and C1 toC3;

FIG. 20 is a cross-sectional view showing another modified example ofthe connecting surface section;

FIG. 21 is a cross-sectional view showing a modified example of the wallsurface;

FIG. 22 is a cross-sectional view showing another modified example of anattachment position of the filter; and

FIG. 23 is a cross-sectional view showing another modified example ofthe wall surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to drawings.

Embodiment

The present embodiment shows an example of a waterproof housing used foran engine ECU (Electric Control Unit) for a vehicle as a waterproofhousing, and an example of an electronic control unit having awaterproof structure used for the engine ECU as a waterproof device.

In addition, in the present embodiment, as shown in FIG. 2 and the like,a penetrating direction of a ventilation hole is referred to as apenetrating direction, and a direction perpendicular to the penetratingdirection is referred to as a perpendicular direction.

An electronic control unit 100 shown in FIGS. 1 and 2 includes, as maincomponents, a circuit board 10 having a substrate 11 to which electronicdevices 12 are installed, a waterproof housing 20 that houses thecircuit board 10, and a breathing filter 24 attached to the waterproofhousing 20. In the present embodiment, in addition to theabove-described components, the electronic control unit 100 includes asealing member 30. Since the filter 24 is integrated with the waterproofhousing 20 in the state where the filter 24 is attached to thewaterproof housing 20, hereinafter, the filter 24 will be described withthe waterproof housing 20.

The electronic devices 12 such as a microcomputer, a power transistor, aresistor, and a capacitor are installed to the substrate 11, in whichwirings including lands as electrodes and via holes for connecting thewirings are formed, thereby providing the circuit board 10 in which acircuit is configured. In the present embodiment, the electronic devices12 include a pressure sensor.

A connector 13 that electrically connects the circuit configured in thecircuit board 10 to an external device or the like is installed to thesubstrate 11. In the connector 13, a reference numeral 13 a in FIG. 2denotes a housing made of electrical insulating material, and areference numeral 13 b denotes a terminal made of electrical conductingmaterial, a part of which is supported by the housing 13 a. FIG. 2 showsan example that the terminal 13 b of the connector 13 is inserted andinstalled to the substrate 11. However, an installation structure is notlimited to the above example, and a surface mount structure can beapplied. In addition, in FIG. 2, through-holes, into which the terminal13 b is inserted, and the lands are omitted from the substrate 11, andsolder that connects the lands to the terminal 13 b is also omitted.

The waterproof housing 20 is made of metal material such as aluminum andiron or resin material. The waterproof housing 20 houses the circuitboard 10 therein to protect the circuit board 10. The number ofcomponents for configuring the waterproof housing 20 is not specificallylimited. The waterproof housing 20 may include one component, or mayinclude multiple components.

In the present embodiment, as shown in FIG. 2, the waterproof housing 20includes a box-shaped case 21, one surface of which is opened, and ashallow base 22 that closes the opening portion of the case 21. The case21 and the base 22 are fixed to each other so that the waterproofhousing 20 having an internal space, in which the circuit board 10 ishoused, is formed. A dividing direction of the waterproof housing 20including the case 21 and the base 22 is not specifically limited. Inthe present embodiment, as shown in FIG. 2, the waterproof housing 20 isdivided into two parts, that is, the case 21 and the base 22, in thepenetrating direction.

As shown in FIG. 3, the waterproof housing 20 has a ventilation hole 23,and the waterproof filter 24 that covers the ventilation hole 23 isattached to the waterproof housing 20. The ventilation hole 23penetrates through a housing wall 21 c of the waterproof housing 20 froman inner surface 21 b to an outer surface 21 a of the housing wall 21 cin a penetrating direction thereof.

The ventilation hole 23 is an air hole for ventilating the internalspace and the external space of the waterproof housing 20. A formedposition of the ventilation hole 23 is not specifically limited. Byforming the ventilation hole 23, even when a temperature inside oroutside the waterproof housing 20 is changed and thus a pressure insideor outside the waterproof housing 20 is changed, the pressure inside thewaterproof housing 20 becomes substantially the same as the pressureoutside the waterproof housing 20, and deformation of the case 21 andthe base 22 is suppressed.

Furthermore, since the pressure inside the waterproof housing 20 becomessubstantially the same as the pressure outside the waterproof housing 20(i.e., atmosphere pressure) by forming the ventilation hole 23, thepressure sensor as the electronic device 12 installed to the substrate11 can operate normally.

The ventilation hole 23 can be formed when the waterproof housing 20 isfabricated by casting such as press molding and aluminum die-casting,and injection molding of resin. Alternatively, the ventilation hole 23can be formed by a post-processing step by the use of a drill or a laserafter the waterproof housing 20 is fabricated.

In contrast, the filter 24 is formed to suppress a decrease in awaterproof property of the waterproof housing 20, which is resulted fromthe formation of the ventilation hole 23 for adjusting a pressure. Thefilter 24 is formed to be generally planar (sheet-like shape) and ismade of water-shedding fibrous material so as to restrain liquid such aswater from passing through the filter 24 and make only gas pass throughthe filter 24. The filter 24 has the waterproof property enough towithstand a high-pressure water flow, such as a vehicle washer. In thepresent embodiment, since the electronic control unit 100 is arranged inan engine room of the vehicle, the filter 24 has an oil-sheddingproperty in addition to the water-shedding property and the ventilationproperty.

In the present embodiment, as shown in FIG. 3, the ventilation hole 23is formed in the housing wall 21 c of the case 21 of the waterproofhousing 20 along a thickness direction of the case 21 from the innersurface 21 b to the outer surface 21 a. More specifically, oneventilation hole 23 is formed in the bottom of the box-shaped case 21.The filter 24 is attached to the inner surface 21 b of the case 21 withadhesive tape (not shown) so as to close the ventilation hole 23.

In the case 21 and the base 22 configuring the waterproof housing 20, acutting portion (not shown) for the connector, which corresponds to thehousing 13 a of the connector 13, is formed. The substrate 11 includingthe electronic devices 12 and a part of the terminal 13 b of theconnector 13, which is connected to the substrate 11, are housed in thewaterproof housing 20. The other part of the terminal 13 b of theconnector 13, which is connected to an external connector, is exposed tothe outside of the waterproof housing 20.

Although not shown, in the state where the case 21 is fixed to the base22, a part of the substrate 11 is directly or indirectly sandwichedbetween the case 21 and the base 22, and thus, the circuit board 10 issupported at a predetermined position in the waterproof housing 20. Inthe present embodiment, in the fixing state of the circuit board 10, athickness direction of the substrate 11 configuring the circuit board 10corresponds to the penetrating direction.

The waterproof sealing member 30 is arranged at a position where thecase 21 and the base 22 are opposed to each other in peripheral portionsof the case 21 and the base 22. Moreover, the sealing member 30 isarranged at a position where the housing 13 a of the connector 13 andthe case 21 are opposed to each other, and at a position where thehousing 13 a of the connector 13 and the base 22 are opposed to eachother.

Next, a fixation structure of the filter 24 to a wall surface 25 of thecase 21 having the ventilation hole 23, which is a characterizingportion of the present invention, will be described.

As shown in FIGS. 4 and 5, the case 21 includes the wall surface 25 as aportion configuring the ventilation hole 23, that is, a portionconfiguring a wall surface of the ventilation hole 23.

The wall surface 25 includes a first slope surface section 25 a and acylindrical surface section 25 b. The inclination of the first slopesurface section 25 a and that of the cylindrical surface section 25 bare different from each other with respect to the perpendiculardirection.

The first slope surface section 25 a is a sloping portion of the wallsurface 25. The first slope surface section 25 a is formed such that across-sectional area thereof is increased with distance from the filter24 in the penetrating direction. That is, the first slope surfacesection 25 a has an increasing cross-sectional area, which progressivelyincreases from an inner end to an outer end of the first slope surfacesection 25 a toward the outer surface 21 a of the housing wall 21 c inthe penetrating direction of the ventilation hole 23. In contrast, thecylindrical surface section 25 b is a portion of the wall surface 25,which is formed such that a cross-sectional area thereof is constant inthe penetrating direction. That is, the cylindrical surface section 25 bhas a generally constant cross-sectional area along an entire extent ofthe cylindrical surface section 25 b. In addition, the cross-sectionalarea of each of the first slope surface section 25 a and the cylindricalsurface section 25 b is a cross-sectional area along the perpendiculardirection.

In the present embodiment, the ventilation hole 23 having a circularcross-section along the perpendicular direction is formed by the wallsurface 25. The first slope surface section 25 a is inclined such that arate of change in the cross-sectional area is constant in thepenetrating direction. In other words, the rate of change in thecross-sectional area of the first slope surface section 25 a per unitdistance in the penetrating direction of the ventilation hole 23 isgenerally constant along the entire extent of the first slope surfacesection 25 a. That is, an inclined angle θ1 with respect to theperpendicular direction is constant. It is easy to form the first slopesurface section 25 a with the constant inclined angle θ1 by molding or aprocess after molding, compared with other slope surface sections (referto the following modified examples).

In the penetrating direction, one end (outer end) of the first slopesurface section 25 a forms an outer opening end 25 c, and the other end(inner end) of the first slope surface section 25 a forms a connection25 d. The outer opening end 25 c configures an outer-surface side openend of the ventilation hole 23, and the connection 25 d is connected tothe cylindrical surface section 25 b. The first slope surface section 25a has a rotationally symmetrical structure with respect to a centralaxis 23 c of the ventilation hole 23 having the circular cross-section.The outer opening end 25 c and the connection 25 d, which has a diameteralong the perpendicular direction smaller than that of the outer openingend 25 c, are arranged in a concentric pattern with respect to thecentral axis 23 c. Here, the central axis 23 c is generally parallel tothe penetrating direction of the ventilation hole 23.

In the penetrating direction, one end (outer end) of the cylindricalsurface section 25 b forms the connection 25 d, and the other end (innerend) of the cylindrical surface section 25 b forms an inner opening end25 e. The inner opening end 25 e configures an inner-surface side openend of the ventilation hole 23. In addition, in FIG. 5, t0 denotes apenetration length of the ventilation hole 23, that is, a thickness of aportion in the case 21, in which the ventilation hole 23 is formed. Inother words, t0 denotes a thickness of the housing wall 21 c measured inthe penetrating direction. Moreover, t1 denotes a length of thecylindrical surface section 25 b measured in the penetrating direction.In this manner, the cylindrical surface section 25 b having the lengthof t1 in the penetrating direction and the first slope surface section25 a having a length of (t0-t1) in the penetrating direction are locatedin this order from a side of the inner surface 21 b of the case 21.

The filter 24 is attached to the inner surface 21 b of the case 21 so asto cover the ventilation hole 23, more specifically, so as to close theinner-surface side open end of the ventilation hole 23, i.e., the inneropening end 25 e of the wall surface 25. Thus, a peripheral portion ofthe inner opening end 25 e in the inner surface 21 b of the waterproofhousing 20 is a filter attachment portion 26 to which the filter 24 isattached.

In the present embodiment, as shown in FIG. 4, a shape of the filter 24along the perpendicular direction is a circular shape. In FIGS. 4 and 5,the reference numeral 24 a denotes an exposed portion of the filter 24,which is opposed to the ventilation hole 23, and the reference numeral24 b denotes an outer peripheral end of the filter 24 in theperpendicular direction. If the filter 24 is attached to the filterattachment portion 26 of the case 21 such that the center of the filter24 corresponds to the central axis 23 c of the ventilation hole 23, theouter peripheral end 24 b of the filter 24, the outer opening end 25 cand the connection 25 d of the wall surface 25 are arranged in aconcentric pattern.

As described above, in the present embodiment, the filter attachmentportion 26 is arranged on the inner surface 21 b of the case 21configuring the waterproof housing 20, and the filter 24 is attached tothe inner surface 21 b of the case 21. Therefore, in washing thevehicle, the high-pressure water flow (e.g., water flow of about 8 to 10MPa) of the vehicle washer is not directly poured onto a portion of thecase 21, to which the filter 24 is attached (hereinafter referred to asan attachment part). Accordingly, the peel-off of the sheet-like filter24 due to the high-pressure water flow can be suppressed compared withthe configuration in which the filter 24 is attached to the outersurface 21 a of the case 21 and the high-pressure water flow is directlypoured on the attachment part.

In the case where the filter 24 is attached to the inner surface 21 b ofthe case 21, it is difficult for the high-pressure water flow with asmall incident angle α1 (refer to FIG. 6) with respect to theperpendicular direction to be directly poured on the exposed portion 24a of the filter 24 because of the thickness t0 of the case 21. In otherwords, it is easy for the high-pressure water flow with a large incidentangle α1 to be directly poured on the exposed portion 24 a of the filter24.

In contrast, in the present embodiment, the case 21 has the inclinedfirst slope surface section 25 a as the wall surface 25 of theventilation hole 23. The first slope surface section 25 a is formed suchthat the cross-sectional area thereof is increased with distance fromthe filter 24. For example, as shown in FIG. 6, if high-pressure waterflows 110, 111 are injected toward the case 21 with a large incidentangle α1 (α1=90° in FIG. 6), a part of the high-pressure water flow 110injected to the first slope surface section 25 a is reflected on thefirst slope surface section 25 a and a reflected water flow 112 hitsagainst the high-pressure water flow 111 above (anterior to) the exposedportion 24 a of the filter 24. Thus, an impetus of the high-pressurewater flow 111 that is going to directly hit against the filter 24 isweakened to become a water flow 113 with a low pressure.

Specifically, in the present embodiment, the first slope surface section25 a has the constant inclined angle θ1 and the rotationally symmetricalstructure with respect to the central axis 23 c. Thus, compared with afirst slope surface section 25 a having a constant rate of change in thecross-sectional area thereof and an asymmetrical structure in thepenetrating direction, the reflected water flow 112 which has reflectedon the first slope surface section 25 a concentrates in a narrow regionin the penetrating direction. Therefore, the impetus of thehigh-pressure water flow 111 can be weakened effectively.

Furthermore, in the present embodiment, the filter 24 is attached to thefilter attachment portion 26 arranged on the inner surface 21 b of thecase 21. Therefore, if the high-pressure water flows 110, 111 areinjected, at the beginning of the injection, water 114 is stored in theventilation hole 23 due to at least the impetuses of the high-pressurewater flows 110, 111 with the exposed portion 24 a of the filter 24 usedas an end surface. Since the stored water 114 functions as a cushion,the high-pressure water flows 110, 111 (including the water flow 113)can be restrained from directly hitting against the exposed portion 24 aof the filter 24 despite the incident angle α1, that is, even when theincident angle α1 of each of the high-pressure water flows 110, 111 issmall.

Specifically, in the present embodiment, the wall surface 25 includesthe cylindrical surface section 25 b as a connecting surface sectionthat connects the first slope surface section 25 a with the inneropening end 25 e. The first slope surface section 25 a is located awayfrom the inner-surface side open end of the ventilation hole 23. Asmallest cross-sectional area of the cylindrical surface section 25 b asthe connecting surface section is located at the outer end of thecylindrical surface section 25 b, which is directly connected to theinner end of the first slope surface section 25 a at the connection 25d. The configuration of the present embodiment is compared with theconfiguration in which the one end of the first slope surface section 25a forms the inner opening end 25 e of the wall surface 25. If thecross-sectional area of the ventilation hole 23 at the inner-surfaceside open end (in other words, the attaching structure of the filter 24with respect to the case 21) and the amount of the water 114 stored inthe ventilation hole 23 with the filter 24 used as the end surface arecommon in the two configurations, a depth of the water 114 stored in theventilation hole 23 with the filter 24 used as the end surface can beincreased in the configuration of the present embodiment. Thus, acushioning effect can be improved, and the peel-off of the filter 24 canbe restrained effectively.

As described above, in the waterproof housing 20 according to thepresent embodiment, that is, in the electronic control unit 100, thepeel-off of the filter 24 due to the high-pressure water flows 110, 111can be suppressed compared with the configuration according to therelated art.

If the water 114 remains in the ventilation hole 23 with the filter 24used as the end surface, the ventilation hole 23 is closed by the water114, and thereby, a pressure inside the waterproof housing 20 becomes anegative pressure with respect to a pressure outside the housing 20.Thus, the water 114 may penetrate into the filter 24 or the water 114may be drawn into the inside of the waterproof housing 20. Therefore, itis preferable that the waterproof housing 20, that is, the electroniccontrol unit 100 is installed to the vehicle such that when theinjection of the high-pressure water flows 110, 111 is stopped, thewater 114 flows out of the wall surface 25 by its own weight with theelectronic control unit 100 installed to a predetermined position of thevehicle.

In the case of the wall surface 25 of the present embodiment, forexample, as shown in FIG. 7, the electronic control unit 100 may beinstalled to the vehicle such that the central axis 23 c of theventilation hole 23 extends along a horizontal direction. That is, theelectronic control unit 100 may be installed to the vehicle such thatthe ventilation hole 23 covered by the filter 24 opens in the horizontaldirection. According to such an installation structure, when thehigh-pressure water flows 110, 111 are injected, the water 114 is storedin the ventilation hole 23 (refer to FIG. 6) with the exposed portion 24a of the filter 24 used as the end surface, due to the impetus of thewater flow. When the injection is stopped, the stored water 114 flowsout of the wall surface 25 by its own weight. In addition, thehorizontal direction is a direction perpendicular to a verticaldirection.

In addition to the configuration shown in FIG. 7, for example, theelectronic control unit 100 may be installed to the vehicle such thatthe outer-surface side open end of the ventilation hole 23 is locatedbelow the inner-surface side open end thereof with the central axis 23 cextending along the vertical direction. That is, the electronic controlunit 100 may be installed to the vehicle such that the ventilation hole23 covered by the filter 24 opens downward in the vertical direction.

First Modified Example

In the waterproof housing 20 shown in FIG. 8, that is, in the electroniccontrol unit 100, the first slope surface section 25 a formed in thecase 21 has a slope which is formed such that a rate of change in thecross-sectional area thereof is increased toward the filter 24 in thepenetrating direction. In other words, the first slope surface section25 a is configured such that a rate of change in the cross-sectionalarea thereof per unit distance in the penetrating direction of theventilation hole 23 is increased toward the inner surface 21 b of thehousing wall 21 c. The configurations other than the configuration ofthe first slope surface section 25 a are the same as those shown in FIG.5. In FIG. 8, the first slope surface section 25 a is a sloping surfacehaving a single radius of curvature.

In addition to the effect obtained by the configurations shown in FIG.5, the following effect can be further obtained by adopting the aboveconfiguration.

As shown in FIG. 9A, the high-pressure water 110 with a large incidentangle α1 (α1=90° in FIG. 9A) is reflected on the first slope surfacesection 25 a and the reflected water flow 112 concentrates in a region112 a above (anterior to) the exposed portion 24 a of the filter 24. Byusing the first slope surface section 25 a shown in FIG. 8, the region112 a in the penetrating direction can be narrowed compared with theregion 112 a shown in FIG. 9B, in which the first slope surface section25 a shown in FIG. 5 is used.

Thus, the impetus of the high-pressure water flow 111 (not shown in FIG.9A) that is going to directly hit against the exposed portion 24 a ofthe filter 24 can be effectively weakened by the water flow 112.

Specifically, as well as the configuration shown in FIG. 5, in theconfiguration shown in FIG. 8, the first slope surface section 25 a hasthe rotationally symmetrical structure with respect to the central axis23 c of the ventilation hole 23 having the circular cross-section.Therefore, compared with the configuration, in which the first slopesurface section 25 a has a slope formed such that a rate of change inthe cross-sectional area thereof is increased toward the filter 24 inthe penetrating direction and does not have a single radius ofcurvature, the water flow 112 which has reflected on the first slopesurface section 25 a can concentrate in a narrower region in thepenetrating direction.

Second Modified Example

In the waterproof housing 20 shown in FIG. 10, that is, in theelectronic control unit 100, the first slope surface section 25 a formedin the case 21 has a slope which is formed such that a rate of change inthe cross-sectional area thereof is decreased toward the filter 24 inthe penetrating direction. In other words, the first slope surfacesection 25 a is configured such that a rate of change in thecross-sectional area thereof per unit distance in the penetratingdirection of the ventilation hole 23 is decreased toward the innersurface 21 b of the housing wall 21 c. The configurations other than theconfiguration of the first slope surface section 25 a are the same asthose shown in FIG. 5. In FIG. 10, the first slope surface section 25 ais a sloping surface having a single radius of curvature.

In addition to the effect obtained by the configurations shown in FIG.5, the following effect can be further obtained by adopting the aboveconfiguration.

As shown in FIG. 11, the high-pressure water 110 with a large incidentangle α1 (α1=90° in FIG. 11) is reflected on the first slope surfacesection 25 a and the reflected water flow 112 concentrates in the region112 a above (anterior to) the exposed portion 24 a of the filter 24. Byusing the first slope surface section 25 a shown in FIG. 10, the region112 a in the penetrating direction can be broadened compared with theregion 112 a shown in FIG. 9B, in which the first slope surface section25 a shown in FIG. 5 is used.

In other words, as shown in FIG. 12, with respect to the high-pressurewater flows 110 with various incident angles α1, the reflected waterflow 112 can move toward the upper side of the exposed portion 24 a ofthe filter 24, compared with the first slope surface section 25 a shownin FIG. 5 and the first slope surface section 25 a shown in FIG. 8. Inthis manner, the range of the incident angle α1 of the first slopesurface section 25 a shown in FIG. 10 is broader than those of the firstslope surface section 25 a shown in FIG. 5 and the first slope surfacesection 25 a shown in FIG. 8.

Therefore, the configuration shown in FIG. 10 has a higher degree offreedom for installation (arrangement) of the electronic control unit100 to the vehicle, for example, than the configurations shown in FIGS.5 and 8.

Third Modified Example

In the waterproof housing 20 shown in FIGS. 13 to 15, that is, in theelectronic control unit 100, the wall surface 25 includes a second slopesurface section 25 f as the connecting surface section that connects thefirst slope surface section 25 a with the inner opening end 25 e. Thesecond slope surface section 25 f is formed such that thecross-sectional area thereof is increased toward the inner surface 21 b(filter 24) in the penetrating direction. That is, the second slopesurface section 25 f has an increasing cross-sectional area thatprogressively increases toward the inner surface 21 b of the housingwall 21 c in the penetrating direction of the ventilation hole 23. FIG.13 corresponds to FIG. 5 to which the second slope surface section 25 fis applied, FIG. 14 corresponds to FIG. 10 to which the second slopesurface section 25 f is applied, and FIG. 15 corresponds to FIG. 8 towhich the second slope surface section 25 f is applied.

In addition to the effect obtained by the configurations shown in FIGS.5, 8 and 10, the following effect can be further obtained by adoptingthe above configuration.

By adopting the above configuration, the cross-sectional area of theconnection 25 d between the first slope surface section 25 a and thesecond slope surface section 25 f as the connecting surface section canbe made smaller than the cross-sectional area of the inner opening end25 e. A smallest cross-sectional area of the second slope surfacesection 25 f as the connecting surface section is located at the outerend of the second slope surface section 25 f, which is directlyconnected to the inner end of the first slope surface section 25 a atthe connection 25 d. The above configuration is compared with theconfiguration in which the cylindrical surface section 25 b is used asthe connecting surface section. If the diameter of the exposed portion24 a of the filter 24, which is exposed through the ventilation hole 23having the circular cross-section, is common in the two configurations,in other words, the attaching structure of the filter 24 with respect tothe filter attachment portion 26 is common in the two configurations, itis more difficult for the high-pressure water flow 111 (water flow 113)to be directly poured on the filter 24 in the above configuration.

Furthermore, a depth of the water 114 stored in the ventilation hole 23with the filter 24 used as the end surface can be increased. Therefore,the cushioning effect by the water 114 can be further improved in theabove configuration.

(Test Results)

Next, results of a peel test of the filter will be described. In thepeel test, the inventor formed samples having the configurations shownin FIGS. 5, 8, 10, 13 and 15 and injected the high-pressure water flowwith respect to each sample.

In the peel test, the thickness t0 of the case 21 was set to be 1.4 mm,a diameter D3 of the exposed portion 24 a of the filter 24, which isexposed through the ventilation hole 23 having the circularcross-section, was set to be 4 mm in each sample.

Each of the samples A1 to A6 has the configuration shown in FIG. 5, inwhich the inclined angle θ1 is constant and the cylindrical surfacesection 25 b is used as the connecting surface section. Each of thesamples A7 and A8 has the configuration shown in FIG. 13, in which theinclined angle θ1 is constant and the second slope surface section 25 fis used as the connecting surface section. In addition, in FIG. 17, theconfiguration in which the cylindrical surface section 25 b is used asthe connecting surface section is shown as an example of the samplehaving the constant inclined angle θ1. However, the regulation of adimension or an angle is common to both the configuration in which thecylindrical surface section 25 b is used as the connecting surfacesection and the configuration in which the second slope surface section25 f is used as the connecting surface section.

In the samples A1 to A3, the lengths t1 of the cylindrical surfacesection 25 b are set to be 0.5 mm and the inclined angles θ1 are set tobe 10°, 20°, 30°, respectively. In the samples A4 to A6, the lengths t1of the cylindrical surface section 25 b are set to be 1.0 mm and theinclined angles θ1 are set to be 10°, 20°, 30° respectively. In thesample A7, the inclined angle θ1 is set to be 10° and the length t1 ofthe second slope surface section 25 f is set to be 0.5 mm. In the sampleA8, the inclined angle θ1 is set to be 10° and the length t1 of thesecond slope surface section 25 f is set to be 1.0 mm. Here, the lengtht1 of the second slope surface section 25 f is a length of the secondslope surface section 25 f measured in the penetrating direction.

A diameter (inner diameter) of the connection 25 d between the outer endof the connecting surface section (the cylindrical surface section 25 bor the second slope surface section 25 f) and the inner end of the firstslope surface section 25 a is denoted by D1. As shown in FIG. 16, in thesamples A1 to A6, in which the cylindrical surface section 25 b is usedas the connecting surface section, the diameter D1 was set to be 4 mmthat is the same as the diameter D3. In contrast, in the samples A7 andA8, in which the second slope surface section 25 f is used as theconnecting surface section, the diameter D1 was set to be 2.5 mm that issmaller than the diameter D3.

D2 denotes a distance, which is measured in the perpendicular directionbetween: a cross-point where an imaginary extension line (two-dot chainline in FIG. 17), which extends along and projects from the first slopesurface section 25 a, intersects with a plane of the inner surface 21 bof the housing wall 21 c; and a projecting point of the imaginaryextension line, at which the imaginary extension line projects from theconnection 25 d between the outer end of the connecting surface section(the cylindrical surface section 25 b or the second slope surfacesection 25 f) and the inner end of the slope surface section 25 a. Thedistance D2 can be expressed by the following equation. The imaginaryextension line of the first slope surface section 25 a is a tangent lineof the first slope surface section 25 a.D2={t1²/(1−cos²θ1}^(1/2)×cos θ1  (equation 1)

The distance D2 of each of the samples A1 to A8 shown in FIG. 16 is aresult calculated from the equation 1. As shown in FIG. 16, in each ofthe samples A1, A4, A5, A7 and A8, the distance D2 satisfies arelationship of the following equation.D2>½×D1  (equation 2)

Furthermore, in the sample A4, the distance D2 satisfies a relationshipof the following equation.D2>D1  (equation 3)

That is, as shown in FIG. 16, the sample A4 is formed such that theimaginary extension line of the first slope surface section 25 aintersects with a wall surface of a corresponding connecting surfacesection (i.e., the cylindrical surface section 25 b).

In addition, since the diameter D3 of the exposed portion 24 a of thefilter 24 is 4 mm, as shown in FIG. 16, the sample A8 is also formedsuch that the imaginary extension line of the first slope surfacesection 25 a intersects with a wall surface of a correspondingconnecting surface section (i.e., the second slope surface section 25f).

Each of the samples A1 to A3 and A5 to A7 shown in FIG. 16 is formedsuch that the imaginary extension line of the first slope surfacesection 25 a intersects with the plane of the inner surface 21 b of thehousing wall 21 c in the inner opening end 25 e of the ventilation hole23, that is, the imaginary extension line of the first slope surfacesection 25 a does not intersect with the corresponding connectingsurface section. In the samples A1 to A3 and A5 to A7, a minimumdistance between the cross-point where the imaginary extension line ofthe first slope surface section 25 a intersects with the plane of theinner surface 21 b of the housing wall 21 c and the inner opening end 25e of the ventilation hole 23 is denoted by D4 (refer to FIG. 17). Asshown in FIG. 16, in the samples A1 to A3 and A5 to A7, the minimumdistance D4 is set to be 1 mm or more in the samples A1, A2, A5 and A6,and the minimum distance D4 is set to be less than 1 mm in the samplesA3 and A7. Specifically, the minimum distance D4 is less than 0.5 mm inthe sample A7.

As shown in FIG. 10, a sample B has the first slope surface section 25 aformed such that a rate of change in the cross-sectional area thereof isdecreased toward the filter 24 in the penetrating direction, and thecylindrical surface section 25 b as the connecting surface section. Inthe sample B, as shown in FIG. 18, the radius of curvature R of thefirst slope surface section 25 a (i.e., first slope portion in FIG. 18)was set to be 0.7, and the length t1 of the cylindrical surface section25 b was set to be 0.7 mm.

As shown in FIG. 8, a sample C1 has the first slope surface section 25 aformed such that a rate of change in the cross-sectional area thereof isincreased toward the filter 24 in the penetrating direction, and thecylindrical surface section 25 b as the connecting surface section. Asshown in FIG. 15, each of samples C2 and C3 has the first slope surfacesection 25 a formed such that a rate of change in the cross-sectionalarea thereof is increased toward the filter 24 in the penetratingdirection, and the second slope surface section 25 f as the connectingsurface section. In the sample C1, as shown in FIG. 18, the radius ofcurvature R was set to be 0.7, and the length t1 of the cylindricalsurface section 25 b was set to be 0.7 mm. As shown in FIG. 18, in thesample C2, the radius of curvature R was set to be 0.9, and the lengtht1 of the second slope surface section 25 f was set to be 0.5 mm. In thesample C3, the radius of curvature R was set to be 0.4, and the lengtht1 of the second slope surface section 25 f was set to be 1.0 mm.Furthermore, in the samples C2 and C3 having the second slope surfacesection 25 f, the diameter D1 of the connection 25 d between the secondslope surface section 25 f and the first slope surface section 25 a wasset to be 2.5 mm.

Moreover, as a comparative object of the samples A1 to A8, B and C1 toC3, a sample which has a ventilation hole having a circularcross-section with the constant diameter D3 at any position in thepenetrating direction, in which the thickness t0 is 1.4 mm and thediameter D3 is 4 mm, was prepared.

In the above-described samples A1 to A8, B, C1 to C3 and the comparativesample, the filter 24 was attached to the filter attachment portion 26on the inner surface 21 b of the case 21 with adhesive tape having acircular shape with an inner diameter of 8.89 mm and an outer diameterof 19.05 mm. That is, the area of the filter attachment portion 26(attachment area of the filter 24) was set to be 222.95 mm².

The pressure of the high-pressure water flow was set to be 8 MPa. Theincident angle α1 was set to be 90°, that is, the high-pressure waterflow was injected to each sample in the penetrating direction of theventilation hole 23, and a peeled area of each sample was measured. Ineach sample, three samples were prepared. Each of values shown in FIG.19 is an average value of the three samples in each sample.

First, the samples A1 to A8 having the constant inclined angle θ1 willbe considered.

As shown in FIG. 19, it became clear from the comparison between thesamples A1 to A3 having the common length t1 and the comparison betweenthe samples A4 to A6 having the common length t1, that the peeled areabecomes small as the inclined angle θ1 is decreased.

It is considered that this is because 1) it becomes difficult for thehigh-pressure water flow 110 which is not reflected on the first slopesurface section 25 a and flows along the first slope surface section 25a to be poured on the exposed portion 24 a of the filter 24, and 2) theimpetus of the high-pressure water flow 111 can be weakened due to thewater flow 112 (refer to FIG. 6) which has reflected on the first slopesurface section 25 a because the area of the first slope surface section25 a is increased as the inclined angle θ1 is decreased.

Furthermore, it became clear from the comparison between the samples A1and A4 having the common inclined angle θ1, the comparison between thesamples A2 and A5 having the common inclined angle θ1, and thecomparison between the samples A3 and A6 having the common inclinedangle θ1, that the peeled area becomes small as the length t1 of thecylindrical surface section 25 b is increased. Similarly, it becameclear from the comparison between the samples A7 and A8 having thecommon inclined angle θ1, that the peeled area becomes small as thelength t1 of the second slope surface section 25 f is increased.

It is considered that this is because 1) if the water 114 stored in theventilation hole 23 with the filter 24 used as the end surface is aconstant amount, the depth of the water 114 can be increased as thelength t1 of the connecting surface section (the cylindrical surfacesection 25 b or the second slope surface section 25 f) is increased andthe cushioning effect can be improved, and 2) it becomes difficult forthe water flow flowing along the first slope surface section 25 a to bedirectly poured on the exposed portion 24 a of the filter 24 attached tothe filter attachment portion 26 on the inner surface 21 b of the case21 as the length t1 of the connecting surface section is increased.

In the samples A4 to A6 and A8, in which the peeled area is small, thelength t1 of the connecting surface section (the cylindrical surfacesection 25 b or the second slope surface section 25 f) is 1.0 mm. In thesamples A1 to A3 and A7, the length t1 is 0.5 mm.

Accordingly, it is clear that if the length t1 of the connecting surfacesection (the cylindrical surface section 25 b or the second slopesurface section 25 f) is equal to or larger than one-half of thethickness t0 of the waterproof housing 20 (the case 21), the peel-off ofthe sheet-like filter 24 due to the high-pressure water flow can besuppressed compared with the configuration where t1<(t0/2).

In the samples A1, A4, A5 and A8 of five samples A1, A4, A5, A7 and A8,which satisfy the relationship of the above equation 2, it became clearthat the peeled area becomes drastically small compared with thecomparative sample.

It is considered that this is because 1) the water flows which are notreflected on the surface of the first slope surface section 25 a andflow along the first slope surface section 25 a formed to surround theexposed portion 24 a of the filter 24 hit against each other and theimpetuses of the water flows are weakened before the water flows arepoured on the filter 24, and 2) the impetus of the high-pressure waterflow 111 (the water flow 113) that is going to directly hit against thefilter 24 is weakened due to the water flow flowing along the firstslope surface section 25 a.

Especially, in the samples A4 and A8 configured such that the imaginaryextension line of the first slope surface section 25 a intersects withthe wall surface of the corresponding connecting surface section, itbecame clear that the peeled area becomes drastically small comparedwith the comparative sample.

It is considered that this is because the water flow flowing along thefirst slope surface section 25 a of the high-pressure water flow 110hits against the wall surface of the connecting surface section (thecylindrical surface section 25 b or the second slope surface section 25f) before the water flow is poured on the filter 24 and the impetus ofthe water flow is further weakened before the water flow is poured onthe filter 24.

Moreover, although the inclined angle θ1 of 10° is common in the samplesA4 and A8, the peeled area of the filter 24 in the sample A8 having thesecond slope surface section 25 f is smaller than that in the sample A4having the cylindrical surface section 25 b.

It is considered that this is because 1) the cross-sectional area of theconnection 25 d between the first slope surface section 25 a and theconnecting surface section is smaller than the cross-sectional area ofthe inner opening end 25 e of the ventilation hole 23 and thehigh-pressure water flow 111 (the water flow 113) which directly hitsagainst the filter 24 is reduced, and 2) the depth of the water 114stored in the ventilation hole 23 with the filter 24 used as the endsurface can be increased and the cushioning effect can be furtherimproved.

In contrast, although the inclined angle θ1 of 10° is common in thesamples A4 and A7, the peeled area of the filter 24 in the sample A7having the second slope surface section 25 f is larger than that in thesample A4 having the cylindrical surface section 25 b and issubstantially the same as that in the comparative sample.

As shown in FIG. 16, in the sample A7, the minimum distance D4 betweenthe cross-point where the imaginary extension line of the first slopesurface section 25 a intersects with the plane of the inner surface 21 bof the housing wall 21 c and the inner opening end 25 e of theventilation hole 23 is 0.41 mm. Thus, the water flow flowing along thefirst slope surface section 25 a is directly poured in the vicinity ofthe attachment part (the filter attachment portion 26 of the case 21) inthe exposed portion 24 a of the filter 24. It is considered that as aresult, the effect obtained by using the second slope surface section 25f is canceled, and the peeled area of the filter 24 in the sample A7becomes larger than that in the sample A4.

It is clear from the result of the sample A3 having the minimum distanceD4 of 0.87 mm as shown in FIG. 16, that the water flow flowing along thefirst slope surface section 25 a is poured in the vicinity of theattachment part (the filter attachment portion 26 of the case 21) in theexposed portion 24 a of the filter 24 so that the peeled area isincreased.

Accordingly, it is preferable that the above-described minimum distanceD4 is 1 mm or more in the configuration in which the imaginary extensionline of the first slope surface section 25 a intersects with the planeof the inner surface 21 b of the housing wall 21 c in the inner openingend 25 e of the ventilation hole 23. By adopting such a configuration,the water flow flowing along the first slope surface section 25 a ispoured on a part separately from the attachment part of the filter 24.Thus, the peel-off of the sheet-like filter 24 due to the high-pressurewater flow 110 can be suppressed.

Based on the above results, as shown in FIGS. 5 and 13, in theconfiguration in which the penetrating direction of the ventilation hole23 having the circular cross-section is perpendicular to the innersurface 21 b and the outer surface 21 a of the case 21, and the wallsurface 25 includes the first slope surface section 25 a with theconstant inclined angle θ1 and the connecting surface section (thecylindrical surface section 25 b or the second slope surface section 25f) and has rotational symmetry about the central axis 23 c of theventilation hole 23, it is preferable that the wall surface 25 is formedto satisfy the relationship of the equation 2. It is most preferablethat the wall surface 25 is formed such that the imaginary extensionline of the first slope surface section 25 a intersects with the wallsurface of the connecting surface section (the cylindrical surfacesection 25 b or the second slope surface section 25 f).

Moreover, it is preferable that the length t1 of the connecting surfacesection is equal to or larger than one-half of the thickness t0 of thecase 21. Furthermore, it is preferable that the wall surface 25 isformed such that the minimum distance D4 between the cross-point wherethe imaginary extension line of the first slope surface section 25 aintersects with the plane of the inner surface 21 b of the housing wall21 c and the inner opening end 25 e of the ventilation hole 23 becomes 1mm or more.

In contrast, it is clear from the comparison with the comparative sampleshown in FIG. 19, that the peeled area in the sample B can be decreasedcompared with the related art.

In addition, it is clear from the comparison with the comparative sampleshown in FIG. 19, that the peeled area in each of the samples C1 to C3can be decreased compared with the related art.

It is clear from the comparison between the samples B and C1 having thecylindrical surface section 25 b and the common thickness t1, that thesample C1 having the first slope surface section 25 a that is formedsuch that a rate of change in the cross-sectional area thereof isincreased toward the filter 24 in the penetrating direction is effectivefor suppressing the peel-off of the filter 24 with respect to thehigh-pressure water flow with a large incident angle α1, compared withthe sample B.

Furthermore, it is clear from the comparison between the samples C1 toC3, that the configuration in which the second slope surface section 25f is used as the connecting surface section is effective for suppressingthe peel-off of the sheet-like filter 24 due to the high-pressure waterflow 110, compared with the configuration in which the cylindricalsurface section 25 b is used as the connecting surface section.

Furthermore, it is clear from the comparison between the samples C2 andC3, that the configuration in which the length t1 of the connectingsurface section is equal to or larger than one-half of the thickness t0of the case 21 is more effective for suppressing the peel-off of thefilter 24.

In the samples C1 to C3, the first slope surface section 25 a is formedsuch that a rate of change in the cross-sectional area thereof isincreased toward the filter 24 in the penetrating direction. Thus, itbecomes difficult for the water flow flowing along the first slopesurface section 25 a to be directly poured on the exposed portion 24 aof the filter 24.

Hereinbefore, the preferred embodiment of the present invention isdescribed. However, the present invention is not limited to theabove-described embodiment, and various changes can be made withoutdeparting from the scope of the invention.

The present embodiment shows the example of the waterproof housing 20used for the engine ECU for a vehicle as the waterproof housing, and theexample of the electronic control unit 100 having a waterproof structureused for the engine ECU for a vehicle as the waterproof device.Moreover, the circuit board 10 is shown as an example of the electronicdevice 12 housed in the waterproof housing 20. However, the electronicdevice 12 is not limited to the circuit board 10, and the use of thewaterproof housing 20 or the waterproof structure is not limited to theabove-described example. For example, the waterproof housing 20described in the present embodiment may be applied to a coverconfiguring a headlight of a vehicle. In this case, a lamp or the likecorresponds to the electronic device 12.

In the present embodiment, the wall surface 25 of the waterproof housing20 (the case 21) includes the cylindrical surface section 25 b or thesecond slope surface section 25 f as the connecting surface section.However, as shown in FIG. 20, the configuration in which the cylindricalsurface section 25 b and the second slope surface section 25 f are usedas the connecting surface section may be applied. In such aconfiguration, it is preferable that the wall surface 25 is formed tosatisfy the relationship of the equation 2. It is most preferable thatthe wall surface 25 is formed such that the imaginary extension line ofthe first slope surface section 25 a intersects with the wall surface ofthe connecting surface section (the cylindrical surface section 25 b andthe second slope surface section 25 f). Moreover, it is preferable thatthe length t1 of the connecting surface section is equal to or largerthan one-half of the thickness t0 of the case 21. Furthermore, it ispreferable that the wall surface 25 is formed such that the minimumdistance D4 between the cross-point where the imaginary extension lineof the first slope surface section 25 a intersects with the plane of theinner surface 21 b of the housing wall 21 c and the inner opening end 25e of the ventilation hole 23 becomes 1 mm or more.

The configuration in which the wall surface 25 does not have theconnecting surface section may be applied. In an example shown in FIG.21, the wall surface 25 has only the first slope surface section 25 a(the configuration shown in FIG. 5 is illustrated in FIG. 21 as anexample). However, by forming the connecting surface section such as thecylindrical surface section 25 b or the second slope surface section 25f, the cushioning effect of the stored water 114 with the filter 24 usedas the end surface can be improved as described above.

In the present embodiment, the filter attachment portion 26 to which thefilter 24 is attached is arranged on the inner surface 21 b. However, aslong as the ventilation hole 23 is covered by the filter 24, theconfiguration in which the filter attachment portion 26 is arranged at aposition nearer the inner surface 21 b than the first slope surfacesection 25 a and the filter 24 is attached to the filter attachmentportion 26 may be applied. For example, as shown in FIG. 22, theconfiguration in which the wall surface 25 includes the filterattachment portion 26 having an attachment surface perpendicular to thepenetrating direction between the first slope surface section 25 a andthe inner opening end 25 e may be applied.

In the example shown in FIG. 22, the wall surface 25 includes the firstslope surface section 25 a, a first cylindrical surface section 25 g, aperpendicular section 25 h and a second cylindrical surface section 25i, which are arranged in this order from a side of the outer opening end25 c. One end of the first cylindrical surface section 25 g is connectedto the first slope surface section 25 a. The first cylindrical surfacesection 25 g is a portion with a constant cross-sectional area in thepenetrating direction. The perpendicular section 25 h protrudes towardthe central axis 23 c of the ventilation hole 23 from the firstcylindrical surface section 25 g, and has a surface perpendicular to thepenetrating direction. A part of the perpendicular section 25 h is usedas the filter attachment portion 26. The second cylindrical surfacesection 25 i is a portion with a constant cross-sectional area in thepenetrating direction, and connects the perpendicular section 25 h withthe inner opening end 25 e.

In the example shown in FIG. 22, a length of the first cylindricalsurface section 25 g is larger than a thickness of the filter 24 in thepenetrating direction. That is, a length t2 from a surface(outer-surface side) of the filter 24 to the connection 25 d has apredetermined length with the filter 24 attached to the filterattachment portion 26. If the length t1 in the above configuration inwhich the filter 24 is attached to the filter attachment portion 26 onthe inner surface 21 b is replaced with the length t2, and the planewith which the imaginary extension line of the first slope surfacesection 25 a intersects is considered to be the same position as thesurface (outer-surface side) of the filter 24 in the penetratingdirection, the configuration is similar to the configuration (FIG. 5)described in the present embodiment. Therefore, if the preferredembodiment in the configuration shown in FIG. 5 is applied to FIG. 22,the effect corresponding to the effect obtained by the configurationshown in FIG. 5 can be obtained.

In the present embodiment, the first slope surface section 25 aconfigures the outer opening end 25 c in the wall surface 25. However,as shown in FIG. 23, for example, the configuration in which the wallsurface 25 includes a cylindrical surface section 25 j that connects theouter opening end 25 c with the first slope surface section 25 a may beapplied. The cylindrical surface section 25 j is a portion having across-sectional area that is the same as the cross-sectional area of theouter-surface side end portion of the first slope surface section 25 aand extending in the penetrating direction.

Although the wall surface 25 has the rotational symmetry about thecentral axis 23 c of the ventilation hole 23 in the present embodiment,the wall surface 25 may have non-rotational symmetry about the centralaxis 23 c of the ventilation hole 23. However, as described above, it ispreferable that the wall surface 25 has the rotational symmetry.

Although the cross-sectional shape of the ventilation hole 23 is thecircular shape in the present embodiment, the cross-sectional shape isnot limited to the circular shape. The cross-sectional shape of theventilation hole 23 may be a polygonal shape such as a rectangularshape.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments and constructions. The invention isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, which arepreferred, other combinations and configurations, including more, lessor only a single element, are also within the spirit and scope of theinvention.

What is claimed is:
 1. An electronic apparatus for a vehicle, comprising: at least one electronic device; a waterproof housing that receives the at least one electronic device in an interior of the waterproof housing, wherein a ventilation hole penetrates through a housing wall of the waterproof housing from an inner surface to an outer surface of the housing wall in a penetrating direction thereof to communicate between an outside and an inside of the waterproof housing; and a filter that is generally planar and is attached to a filter attachment portion of the housing wall to cover the ventilation hole, wherein: a wall surface of the ventilation hole includes a slope surface section that has an increasing cross-sectional area, which progressively increases from an inner end to an outer end of the slope surface section toward the outer surface of the housing wall in the penetrating direction of the ventilation hole; a distance between the filter attachment portion and the outer surface of the housing wall measured in the penetrating direction of the ventilation hole is larger than a distance between the inner end of the slope surface section and the outer surface of the housing wall measured in the penetrating direction of the ventilation hole; and the slope surface section is configured such that a rate of change in the cross-sectional area of the slope surface section per unit distance in the penetrating direction of the ventilation hole is increased toward the inner surface of the housing wall.
 2. The electronic apparatus according to claim 1, wherein: the filter attachment portion is located in the inner surface of the housing wall around an inner opening end of the ventilation hole, which opens in the inner surface of the housing wall.
 3. The electronic apparatus according to claim 2, wherein: the wall surface of the ventilation hole further includes a connecting surface section that has an outer end, which is directly connected to the inner end of the slope surface section at a connection, and an inner end, which forms the inner opening end of the ventilation hole; and a smallest cross-sectional area of the connecting surface section is located at the outer end of the connecting surface section, which is directly connected to the inner end of the slope surface section at the connection.
 4. The electronic apparatus according to claim 3, wherein: the slope surface section is a first slope surface section; and the connecting surface section includes a second slope surface section, which has an increasing cross-sectional area that progressively increases toward the inner surface of the housing wall in the penetrating direction of the ventilation hole.
 5. The electronic apparatus according to claim 3, wherein the connecting surface section includes a cylindrical surface section, which has a generally constant cross-sectional area along an entire extent of the cylindrical surface section.
 6. The electronic apparatus according to claim 2, wherein: the wall surface includes the filter attachment portion having an attachment surface perpendicular to the penetrating direction of the ventilation hole between the slope surface section and the inner opening end.
 7. An electronic apparatus for a vehicle, comprising: at least one electronic device; a waterproof housing that receives the at least one electronic device in an interior of the waterproof housing, wherein a ventilation hole penetrates through a housing wall of the waterproof housing from an inner surface to an outer surface of the housing wall in a penetrating direction thereof to communicate between an outside and an inside of the waterproof housing; and a filter that is generally planar and is attached to a filter attachment portion of the housing wall to cover the ventilation hole, wherein a wall surface of the ventilation hole includes a slope surface section that has an increasing cross-sectional area, which progressively increases from an inner end to an outer end of the slope surface section toward the outer surface of the housing wall in the penetrating direction of the ventilation hole, a distance between the filter attachment portion and the outer surface of the housing wall measured in the penetrating direction of the ventilation hole is larger than a distance between the inner end of the slope surface section and the outer surface of the housing wall measured in the penetrating direction of the ventilation hole, the slope surface section is configured such that a rate of change in the cross-sectional area of the slope surface section per unit distance in the penetrating direction of the ventilation hole is decreased toward the inner surface of the housing wall, the filter attachment portion is located in the inner surface of the housing wall around an inner opening end of the ventilation hole, which opens in the inner surface of the housing wall, the wall surface of the ventilation hole further includes a connecting surface section that has an outer end, which is directly connected to the inner end of the slope surface section at a connection, and an inner end, which forms the inner opening end of the ventilation hole, and a smallest cross-sectional area of the connecting surface section is located at the outer end of the connecting surface section, which is directly connected to the inner end of the slope surface section at the connection.
 8. The electronic apparatus according to claim 7, wherein: the slope surface section is a first slope surface section; and the connecting surface section includes a second slope surface section, which has an increasing cross-sectional area that progressively increases toward the inner surface of the housing wall in the penetrating direction of the ventilation hole.
 9. The electronic apparatus according to claim 7, wherein the connecting surface section includes a cylindrical surface section, which has a generally constant cross-sectional area along an entire extent of the cylindrical surface section. 